A life member of The Actors Studio,[5] Winfield carved out a diverse career in film, television, theater and voiceovers by taking groundbreaking roles at a time when black actors were rarely cast. He first appeared in the 1965 Perry Mason episode, "The Case of the Runaway Racer," as Mitch, a race car mechanic. His first major feature film role was in the 1969 film The Lost Man starring Sidney Poitier. Winfield first became well-known to television audiences when he appeared for several years opposite Diahann Carroll on the groundbreaking television seriesJulia. Filmed during a high point of racial tensions in the United States, the show was unique in featuring a black female as the central character. He also starred as Martin Luther King, Jr. in the 1978 miniseriesKing.

^Garfield, David (1980). "Appendix: Life Members of The Actors Studio as of January 1980". A Player's Place: The Story of The Actors Studio. New York: Macmillan Publishing Co., Inc. p. 280. ISBN0-02-542650-8.